I'm equally interested in both sides, but spend the majority of my time on my father's side, for two reasons. Firstly, my mother knew much more about her family, so I already had a head-start; my father knew essentially nothing. Secondly, my mother had a couple of unusual surnames on her side, so it was pretty easy going. I quickly teamed up with a distant relative who had done most of the work already!
But I also have ethnic problems. My wife is Thai of Chinese extraction. It took a long time to figure out her father's true surname, which had been "Thai-ized" when he emigrated from China, but having done that, I now know that she is descended from Emperor Huang Di, who lived about 2000BC. I bet no-one else has been able to go back so far

. Of course, I have the minor issue of filling in about 100 or so missing generations.
Cheers
Tim